sintering wire mesh

[kevlar49]

Does anyone know any good references for learning how wire mesh is sintered? If the mesh is 300-series stainless steel, to get good bonding, is it recommended to sinter in a vacuum or hydrogen environment? What is typically used to prevent sintering to the hardware. I was thinking of a BN coating. Someone suggested using a silicon semiconductor wafer (might get expensive).

 

[EdStainless]

use alumina plates, very dry hydrogen atmosphere (-60C dew point), and a higher than normal anneal temp (2100F).
We used to do stacks of mesh and then roll it to crush them in order to get the pore size that we wanted.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[btrueblood]

Ed,

Do you acid etch the alumina after each run? Does the alumina tend to collect smut over time if you don't?

kevlar, boron nitride spray worked well to prevent binding on metallic tooling at brazing temp's. for us (up to 1950 F), but I doubt it would work well for ceramic, nor be necessary. Why not just buy Rigimesh or similar products from a mill?

 

[kevlar49]

btrueblood,

sorry need to clarify. I meant BN spray metal plates not ceramic plates. To answer your other question, we want to perform this operation in-house. What is the smut from?

Do you think BN spray on the metal plates in contact with the wire mesh would work well?

 

[btrueblood]

Kev,

We would see smut build up on our brazing tooling, enough to where the braze alloy would start to wet the alumina. I think this was nickel/gold braze alloy, the smut was likely just surface oxides of the metals being driven off at high temperatures, and "plating" the adjacent alumina surfaces. Not sure, can't recall, but this was likely more an issue with vacuum brazing, not H2 atmosphere.

BN spray-on coating would likely rub off under the compression loading I expect you will put to the mesh stack. You'd want something more monolithic, and unlikely to fracture/spall when compressing the stack. Alumina would be a good choice; again, I don't know if smut would be an issue - especially if using a H2 atmosphere vs. vacuum.

 

[EdStainless]

We used Alumina plates under the stacks of mesh. At 2100-2150F they settled together nicely.
You could use BN spray on the plates. But BN is a mess to work with. I like it, but it will get on everything.
We saw the plates darken, but it wasn't much.
I never tried it in a vacuum.
We were making a filter, before there were any of these commercially available (for air bag inflators).

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube